1. Field of the Invention
This invention relates to a semiconductor device such as a MOS transistor (a metal oxide semiconductor field-effect transistor). This invention also relates to a method of fabricating a semiconductor device.
2. Description of the Related Art
In MOS transistors (metal oxide semiconductor field-effect transistors) formed on silicon substrates, hot carriers decrease transistor performances. An LDD (lightly doped drain) structure is effective in suppressing or preventing hot-carriers-caused decreases in transistor performances.
Japanese published unexamined patent application 9-69628 discloses a MOS transistor having such an LDD structure. The MOS transistor in Japanese application 9-69628 tends to be unreliable during operation at a high drive voltage. In addition, the MOS transistor in Japanese application 9-69628 tends to be unable to withstand a high drive voltage.
Japanese published unexamined patent application 5-93922 discloses a MOS transistor having a drift channel structure. The drift channel structure enables the MOS transistor to withstand a high drive voltage. The MOS transistor in Japanese application 5-93922 tends to be large in size.